3D imaging is known in the art. Several techniques are commonly used to create such images. U.S. Pat. No. 6,091,905, and U.S. Pat. No. 6,100,517, both assigned to the common assignees of the present invention and incorporated herein by reference, disclose methods and systems for rapidly and easily determining the distance of various points in a scene. The disclosed methods and systems detect reflected radiation, such as infrared (IR) or near infrared (NIR) radiation, to create a depth map. It will be appreciated that further references in the specification to IR may be exemplary; NIR and/or other types of radiation may also be used.
FIGS. 1 and 2, to which reference is now made, illustrate a typical such system and its exemplary output. As shown in FIG. 1A, system 100 comprises an IR generator 10, an IR detector 20 and a compensator 30. FIG. 2 shows exemplary images produced by system 100.
In a typical implementation, IR generator 10 generates IR radiation 15 and directs it at a scene, including, for example, object 40. IR detector 20 detects the intensity of radiation 25 as reflected from object 40. In general, the greater the intensity, the closer the object. FIG. 2 shows an exemplary RGB image 41A of object 40 and matching IR images 45A.
The intensity of radiation 25 detected by IR detector 20 is a function of both the distance to object 40 and its reflective properties. Reflectivity is the fraction of incident radiation reflected by a surface. Some materials, such as glass or polished metal are highly reflective. Other materials, such as matt paint, have lower reflectivity. Therefore, the material of an object can affect the intensity of the images received by IR detector 20.
To compensate for different reflective properties, as disclosed in U.S. Pat. Nos. 6,091,905 and 6,100,517, IR radiation 15 comprises an alternating series of continuous and pulsed radiations. The resulting series of IR images 45 are forwarded to compensator 30 which processes them to compensate for the different reflective properties. Compensator 30 typically divides a grayscale value for the intensity of a pixel during the continuous radiation period by a grayscale value for the same pixel during the period of pulsed radiation, with the quotient between the two being inversely proportional to a calculated value for depth, i.e. D=P/C, where D represents depth, P represents the pixel intensity received during pulsed radiation, and C represents the pixel intensity received during continuous radiation. The higher the value for depth, the closer the object. Compensator 30 produces a series of depth maps 50 based on the input IR images 45. FIG. 2 shows an exemplary depth map 50A corresponding to IR images 45A.